1. Field of the Invention
This invention relates to the detection of pollutants in cooling water employed for indirect cooling of process streams.
2. Description of the Prior Art
It is well known to cool hydrocarbon or chemical process streams by indirect exchange with cooling water in an essentially closed system wherein the cooling water is subsequently passed through a cooling tower and returned to the heat exchangers. In most cases the pressure of the process fluid in the heat exchangers is higher than that of the cooling water. Occasionally, small leaks develop which permit process fluid to escape into and pollute the cooling water. The presence of such pollutants in the cooling water is undesirable for many reasons. If the pollutant is relatively volatile, such as a light hydrocarbon or hydrogen sulfide, it will escape into the atmosphere from the cooling tower, causing objectionable air pollution and possibly presenting a serious fire and explosions hazard. Many contaminants also have the effect of depleting biocides, such as chlorine, in the cooling water. It is, of course, also desirable to avoid loss of valuable process fluids. Hence, it is desired to detect contamination of cooling water as soon as possible and to be able to identify the leaking heat exchanger.
The method employed to date has been simply to visually inspect the bottom pan of a cooling tower periodically, such as once a day or once a shift, to look for contaminants floating on the water. Conventionally, no special measures are applied to detect escape of gases into the cooling water stream, and such contamination has been known to lead to explosions or fires.